Island



G. Rgo. FRENCH.

`(No Model.)

SGRIEIW TAP.

Patented Jan. 9, l1883'.

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FlElll' WITNEEEEEI INVENTDH.

To all whom it may concern y UNITED STATES PATENT OFFICE.

CICERO R. C. FRENCH, OF PROVIDENCE, RHODE ISLAND.

SCREW-TAP.

SPECIFICATION forming part of Letters Patent No. 270,216, dated January 9, 1883.

' Application filed August 3, 1882. (No model.)

Be it known that 1O1cER0 R. C. FRENCH, of the cityand county of Providence, in the State of Rhode Island, have invented certain new and useful Improvements in Screw-Taps, of which the following is a full and correct description, reference being had to the accompanyin g drawings, forming apart of this speciication.

The object of my invention is to make a tap that can be adjusted so as to make up for the usual reduction in size from wear, and that shall insure a perfectly uniform size from the top to the bottom of a hole made iu solid metal as well as in material that is drilled entirely through.

In the drawings, Figure 1 is a representation ofthe tap. Fig. 2 shows the same turned one-qua rter way around. Fig. 3 is a'longitudi- 'nal Asection through the center of the tap in the direction of the line m, Fig. 2.

A is a screw-tap, through the center of which a longitudinal slot, a, is made, extending from the cutting end up through theigtthreaded portion of the tap.

c is a screw madeslightly tapering from its lower end up, and fitted into a hole in the end of the tap A- with a corresponding thread, so

` that as the screw is turned farther into the tap it shall enlarge its size by spreading the two halves of the tap apart. y The outer end of this screw c may be made square to receive a wrench, or it may be slotted for a screwdriver. At a'short distance above the end `of the screw c a hole is made through the center of the tap across the slot a, into which a stayscrew, s, is tted, that part of the screw cou.- sisting ofthe head and neck being fitted to turn easilyin one half of the tap and theother partitted to screw into the other half of the ta p, so that the screw when turned in the right direction shall draw the two parts of the tap together and hold them from being pushed out of place in using.

It has been found very dicuit in furnishing duplicate partsof engine work and other accurately-fitted machinery to secure a good tit at all times', on account of the wearingaway of the tools in use, especially in screw-holes not drilled entirely through the metal, and which have to be tapped with a bottomingplug tap, the end of which, wearing away,V

makes the hole smaller at the bottom than on the outside. This diiculty is entirely over# come with my improvement, for as the tap wears away the stay-screw s can be slightly loosened and the adjusting-screw c turned alittle farther into the end of the tap until it is expanded to itsoriginal size, and, what is' important, the expansion will be greatest at the-end ofthe tap, where the most wear naturally takes place. This feature, it is believed, is not found in any of the expanding taps in use. Y

Having thus described my improvement, what I claim as my invention, and ydesire to secure by Letters Patent, is

1. A tap for cutting screw-threads, having a slot through its center extending from its cutting end up, substantially' as shown and described, and for the purpose set forth.

2. The combination of a screw-tap, slotted- CICERO C. FRENCH.

Witnesses:

FRANK BULLWURT, ROBERT J. HYLAND. 

